Airbag

ABSTRACT

An airbag, in particular a front airbag, includes an outer wall having a front wall and a rear wall (18, 24) and a tether (16) as well as an electrically actuatable activation unit (26) for releasing the tether (16). The tether (16) includes plural tether portions (30, 32) connected to each other via a first tear seam (36). A tension means (40) is coupled to the tether (16) so that it destroys the first tear seam (36) when the activation unit (26) is not actuated.

The present invention is a U.S. National Stage under 35 USC 371 patentapplication, claiming priority to Application No. PCT/EP2019/086040,filed on 18 Dec. 2019; which claims priority from DE 10 2018 133 051.0,filed 20 Dec. 2018, the entirety of both of which are incorporatedherein by reference.

The invention relates to an airbag, in particular a front airbag,comprising an outer wall having a front wall and a rear wall, a tetherprovided inside the airbag and an electrically actuatable activationunit for releasing the tether so that the tether will no longer developa restraining effect, the airbag adopting a large or a small inflationvolume depending on the actuating state of the activation unit.

Those airbags are especially intended to provide an airbag volumeadapted depending on the situation of restraint. Hence, the airbag canadopt two different geometries and two different volumes, depending onwhether or not the tether exerts a restraining effect upon the frontwall.

Moreover, there are recent efforts to specifically influence theinflation behavior and deployment behavior of the airbag during thedeploying operation. This means that portions of the outer wall of theairbag are to be temporarily withheld during the deploying operation soas to promote deployment in different directions, and only afterwardsthe movement of the outer wall in the region restrained before will bereleased. This temporary restraint is obtained in particular by tearseams at tethers which will definitely tear in each case, i.e., duringeach inflating operation.

In future piloted driving, occupants are expected to be possiblyreclined somewhat more in comfort positions than has been common, or theseat is expected to be displaced further rearward than has beenpreviously common. Thus, even larger differences in volume between thevarious airbag configurations must be realized.

It is the object of the invention to provide an airbag that is adaptedto realize large differences in volume in the fully inflated state andwhich, in the actuated activation state, adopts the larger inflationvolume. At the same time, the airbag is intended to be deployed in anoptimized manner.

This object is achieved, in an airbag of the type mentioned at theoutset, in that the tether is composed of plural tether portions coupledto each other via a first tear seam and a tension means which is coupledto the first tear seam at its front end portion (i.e. close to the frontwall) is coupled to the activation unit so that, upon actuation of theactivation unit, the tear seam is destroyed by tension, that is by thetension generated by this movement of the front wall, and, uponinflation and lacking actuation of the activation unit, the first tearseam remains intact and the airbag has the smaller inflation volume.

In the airbag according to the invention, the tether is not simplyreleased by the activation unit or will remain fastened, when theactivation unit is not activated, as was previously the case, but whenthe activation unit is actuated, also tearing of the first tear seamand, thus, temporary restraint of the front wall can be achieved in thecourse of the deployment operation. When the activation unit isactuated, the tether is destroyed and the airbag can adopt the largergeometry with the larger inflation volume.

Preferably, the tension means with the first tear seam is attached tothe tether, i.e., the first tear seam connects at least three parts toeach other, viz. the two tether portions and the tension means.

Well-directed tearing, on the one hand, and maintaining the stability ofthe first tear seam, on the other hand, is achieved by the tension meanshaving a front end, with “front” always meaning closer to the front wallin a state of the airbag theoretically 30 inflated such that no part isdestroyed. From said front end, the tension means initially extends inthe direction of the front wall to overlap the tether. In saidoverlapping area, the tension means with the first tear seam is fastenedto the tether. After the tear seam, the tension means is folded over atan acute angle, with the folded part being no longer fastened by thefirst tear seam. Said folded portion extends in the direction of theactivation unit. The technical effect resulting therefrom is as follows.If the tension means is not released but remains anchored at its rearend, it exerts a so-called “peeling force” upon the tear seam by thechange of direction after the first tear seam. The tear seam is unstablefor such an application of force and will tear, for said peeling forceacts in such a way that it strives for separating the tension means 5from the front wall laterally to the pulling action. If the tensionmeans is no longer held at the rear end, however, this effect of“peeling”, i.e., of the movement of the tension means laterally awayfrom the tether will no longer occur. Then the tear seam is onlyshear-loaded and is sufficiently stable to absorb the shear forces. Thetether remains intact.

The first and second tether portions can extend exclusively side by sidein the area where they are fastened to each other and can be subjectedto tensile load in the opposite direction. This entails the fact that,between the tether portions in the area of the first tear seam, noeffect of “peeling” will occur, but the first tear seam is onlyshear-loaded with respect to the force exerted upon the first tear seamby the tether portions.

The tension means may include a first part which is attached to thetether with the first tear seam in the area of its front end or mergesintegrally into a tether portion in the area of the first tear seam,wherein the tension means includes at least a second part which, in thearea of a rear end of a first part, is optionally releasably fastenedthereto. The term “optionally releasably” means that, depending on theactuation of the activation unit, the first part and the second part canbe released from each other or remain fastened to each other. Thus,further optional releasing allows to achieve an additional temporaryrestraining effect which additionally temporarily controls thedeployment.

In this context, the tension means may bifurcate at the rear end of thefirst part, namely into a second part and a third part extending side byside in the direction of the rear wall and the activation unit, whereinthe second part is permanently arranged at the rear end and the thirdpart is coupled by its rear end to the activation unit, i.e., isreleasable in the area of its anchoring at the rear end. The second partremains anchored to the rear end, however, completely independently ofthe actuating situation of the activation unit. Said anchoring may begenerally present in the area of the module or else of the rear wall.This embodiment enables the movement of the tether and additionally ofthe tension means to be further subdivided so that the tension meanseither will remain stable or will tear. The coupling of the three partsof the tension means is especially as follows. The first part and thesecond part extend in the area where they are fastened to each otherexclusively side by side in a so-called overlapping area, when a tensileforce is applied, i.e., during deployment and inflation of the airbag,and are subjected to tensile-load in the opposite direction. The thirdpart extends from its front end toward the front wall and is fastened bya second tear seam to the first part and the second part. Hence, saidsecond tear seam fastens all three parts of the tension means to eachother. After the second tear seam, the third part is folded over at anacute angle, however, and extends in the direction of the activationunit. Here, as before, in connection with the tether the effect of“peeling” and, thus, the destruction of the second tear seam will occur,when the third part remains anchored and the activation unit is notactuated. When the activation unit is actuated, the second part will notintroduce, because its anchoring is not released, any additional forceinto the second tear seam, and the latter remains intact. In this case,the first and second parts apply a pure shear force to the second tearseam due to the tensile forces acting in the opposite direction. Thisresults in an additional positive effect for the airbag, for optionallyone tear seam at a time can be activated, no matter whether or not theactivation unit is actuated. Thus, for both states of release, thedeployment movements can be influenced, as the front wall is temporarilyrestrained (until the tear seam is destroyed), and a deploying movementto the side or upwards or downwards is supported.

The airbag may comprise a front chamber and a rear chamber which can befluidly coupled and uncoupled by a valve unit. The valve unit is coupledto the tether and is opened by the tether when the activation unit isactuated. Thus, the airbag may either have a small configuration whenthe valve unit is closed, or may have a large volume, when the valveunit is opened upon actuation of the activation unit. The front chamberthen is either also inflated or not inflated.

Preferably, the front chamber rests on the rear chamber. In thenon-inflated state of the front chamber, the front wall of the frontchamber bears on the front wall of the rear chamber. The front chambercan be additionally fastened to the front wall in the non-inflated statevia fixing tear seams. When the valve unit is opened upon actuation ofthe activation unit, said fixing tear seams will tear and the frontchamber will be inflated/filled.

The rear chamber includes a closed front wall except for the valve unitin accordance with the preferred embodiment which, when the activationunit is not actuated, forms a supporting wall for the occupant and onwhich a wall bears that forms the front wall of the non-inflated frontchamber. Said wall is fastened to the front wall of the rear chamber andforms a smaller airbag attached to the rear chamber which then forms thefront chamber.

Two holding means juxtaposed and spaced apart from each other to whichthe tether is coupled can act on the front wall and in the interior ofthe airbag. The front wall is inverted at the holding means to form asmaller inflation volume, wherein, when the activation unit is actuated,the tether is released and the inversion is dropped.

The holding means can be connected to each other inside the airbag via acorset lacing coupled to the tether, when the activation unit is notactuated. A corset lacing is a cross lacing that alternates back andforth between the two holding means.

Further features and advantages of the invention will be obvious fromthe following description and from the following drawings which arereferred to, and wherein:

FIG. 1 shows a side view of an embodiment of the airbag according to theinvention having a small inflation volume and a large inflation volume,

FIG. 2 shows a schematic view of the interior of the airbag according toa first variant comprising a tether and tension means in the startingsituation,

FIG. 3 shows a schematic view of the tether and the tension means withan actuated activation unit and a large airbag volume,

FIG. 4 shows a schematic view of the tether and the tension means with anon-actuated activation unit and a small airbag volume,

FIG. 5 shows a second embodiment in a schematic side view of the airbagaccording to the invention with a large airbag volume,

FIG. 6 shows a front view of the airbag according to the invention inaccordance with a third embodiment having a small airbag volume,

FIG. 7 shows a sectional view in a lateral view across the airbagaccording to FIG. 6 when the activation unit is not actuated; and

FIG. 8 shows a schematic view according to the arrow X in FIG. 7 showinga corset lacing.

FIG. 1 illustrates a front airbag 10 that is accommodated in aninstrument panel 12 of a vehicle and, moreover, is accommodated beingfolded in an airbag module 14. The airbag 10 deploys from the airbagmodule 14 in the case of an imminent or a currently occurring crash.

The airbag 10 may adopt two different configurations, i.e., it may havea small inflation volume (shown in continuous lines) and a largeinflation volume (shown in broken lines). Thus, the airbag 10 may alsoadopt two different geometries.

In particular when an occupant is in a so-called comfort position, i.e.,either has moved the vehicle seat very far backward and/or has stronglyreclined the seatback, the large inflation volume is intended to beavailable, and in the other cases the small inflation volume is intendedto be available.

The airbag 10 includes, in order to be capable of adopting the differentconfigurations, in its interior one or more tethers 16 which arefastened, on the one hand, by their front end 20 to the front wall 18and, on the other hand, are fastened by their rear end 22 either to theairbag module 14 or to the airbag wall, for example to the rear wall 24in the area of the inflation orifice.

For controlling the two different states of the airbag 10, in the airbagmodule 14 an activation unit 26 such as a pyrotechnically working butelectrically operable activation unit 26 is accommodated. The latter iseither activated, viz. actuated or not depending on establishedparameters. In response thereto, the different inflation volumes arerealized. The gas generator 28 for inflating the airbag 10 is especiallya single-stage gas generator, but a multi-stage gas generator may beprovided as well.

In FIG. 1 , the tether 16 and the activation unit 26 are shown veryschematically only, more details are obvious from the FIGS. 2 to 4 .

In advance, it is emphasized, however, that the principle of allembodiments shown consists in obtaining the larger inflation volume whenthe activation unit 26 is actuated.

For the rest, the activation unit is realized, for example, such that itreleases the rear anchoring of a tension means described hereinafter ordestroys the tension means in the area of the rear anchoring so that thetension means is no longer retained.

FIG. 2 illustrates a variant showing the way in which the tether 16 canbe released.

The tether 16 is made up of a first tether portion 30 that is fastenedby the front wall 18 to the front end 20 and of a second tether portion32. The second tether portion 32 is constantly anchored tightly, i.e.,permanently by its rear end 34 in the area of the airbag module. Thefastening can also be realized at the rear wall, such as at theinflation orifice, but also at the gas generator or other parts.

The tether portions 30, 32 are separate originally separated parts whichare connected to each other via a first tear seam 36. For this purpose,the front end region of the tether portion 32 and the rear end region ofthe tether portion 30 are overlapping. Here they form an overlappingregion in which they extend exclusively side by side, i.e., when thetether 16 is subjected to tensile load, there is no deflection into anyregion of the tether portions 30, 32 or in the overlapping region. Thetensile forces applied act in the opposite direction. With sufficienttensile load, the tether portions 30, 32 rather have a linear extensionin a side view, as visible from FIG. 2 , and said linear extension isalso continued in the overlapping region.

A tension means 40 is fastened to the tether 16 by the tear seam 36,hereinafter referred to as first tear seam 36, wherein the tension means40 may equally consist of plural parts, in the present embodiment of afirst part 42 having a front end 44 which extends, from the front end44, initially in parallel to the tether 16, i.e., also in parallel tothe tether portions 30, 32, so as to then extend, after the tear seam36, at an acute angle, in this case under 180° or almost 180°, towardthe rear wall 24 or the module 14.

In the region of the rear end 46 of the first part 42, the tension means40 bifurcates, viz. into a second part 48 and a third part 50, all ofwhich are fastened to each other via a second tear seam 52. Theformation of the tear seam 52 and the position of the individual partscorresponds to the orientation and the position of the correspondingparts at the first tear seam 36. This means that the second part 48extends, with its front end region, above or below the rear end regionof the first part 42 and overlaps the same, wherein there is no changeof direction in this case and both parts 42, 48 extend linearly in aside view, when they are subjected to tensile load.

However, the third part 50 extends starting from its front end 53initially in parallel and overlapping to the overlapping first andsecond parts 42, 48, but then, viz. after the second tear seam 52 andthe corresponding overlapping region of the parts 42, 48, 50 at an acuteangle backwards in the direction of the activation unit 26.

The rear end 54 of the second part 48 is permanently fastened, e.g., onthe airbag or another part of the module such as on the gas generator.The rear end 56 of the third part 50 is coupled to the activation unit26, however, and can be released when the activation unit 26 isactuated. Purely symbolically, this is illustrated so that the rear end56 is received in a displaceable holder 61 which can be released afterbeing displaced (see arrow).

FIG. 2 illustrates the state in which the tether 16 and the tensionmeans 40 are equally substantially tensioned, wherein neither the tether16 nor the tension means 40 is provided in the activated state of thegas generator 28. In this “slightly” inflated state, the portions andparts were explained before. Only in the FIGS. 3 and 4 are states shownwhich are provided after activation of the gas generator.

In the embodiment according to FIG. 3 , the gas generator is ignited,and the activation unit 26 is actuated. This means that the rear end 56of the third part 50 is released, whereas both the rear end 54 of thesecond part 50 and the rear end 34 of the tether 16 remain anchored,because they are fastened either to the airbag or to any other part ofthe airbag module.

When the activation unit 26 is actuated, the second tear seam 52 remainsstable, and tension is applied to the first tear seam 36 via the tensionmeans 40 by the first part 42 and the second part 50 remaining fastenedto each other when the front wall 18 is moved forward in the directionof the occupant. The length of said tension means 40 is configured sothat it is shorter than the distance between the rear end 34 and thetear seam 36 or, in other words, the tension means 40 is tightened,before the portion of the tether 16 between the rear end 34 and thefirst tear seam 36 is tightened.

By deflecting the first part 42 at an acute angle, a force generated bya so-called peeling effect is applied to the tear seam 36. Due to thedeflection, the first part 42 aims at laterally detaching from theoverlapping region of the first tether portion 30 and the second tetherportion 32. In this direction of force, the first tear seam 36 isunstable and breaks so that not only the tension means 40 detaches fromthe tether 16, but also the tether 16 is separated into its twocomponents. This means the tether 16 is destroyed and no longer active,and the two tether portions 30, 32 are no longer fastened to each other,as shown in FIG. 3 .

In this way, the larger airbag volume can be reached. During thedeployment operation, the airbag 10 was restrained for a short time,however, namely when initially the tension upon the tension means 40 istriggered, namely until the destruction of the second tear seam 36 isreached. Thus, the front wall 18 is temporarily prevented from deployingand the inflowing gas deploys other portions of the airbag.

FIG. 4 illustrates the situation when the activation unit 26 is notactuated and, thus, the smaller airbag volume is to be realized. Then,the rear end 56 remains anchored. For the same reason, viz. the peelingeffect, in this case the second tear seam 52 is destroyed so that thefirst part 42 detaches both from the second part 48 and from the thirdpart 50. The tension means 40 is destroyed and exerts no force upon thefirst tear seam 36. This means that there will be no more peelingeffect. The first tear seam 36 is only shear-loaded, and such load willnot result in the destruction of the tear seam 36.

Thus, the tether 16 remains intact and can prevent the front wall 18from moving further in the direction of the occupant.

In the variant according to FIG. 5 , the airbag 10 has a rear chamber 60and a front chamber 62 resting on the rear chamber 60, the front chamber62 being closer to the occupant and being formed by an airbag wall 64which is stitched onto the front wall 18 of the rear chamber 60. Thefront wall 18 also delimits the front chamber 62 especially at its rearend.

The front wall 18 includes one or more overflow openings 66 via which afluid communication can be established between the chambers 60, 62.

A valve unit 68 closes the one or more overflow openings 66 in theinitial state, however. The valve unit 68 can be a fabric portion, forexample, or any other flexible flat component which is located insidethe first chamber 60 and is connected to the front wall 18 via tearseams 70, for example.

The valve unit 68 is actuated by the tether 16 and can be transferredfrom the originally closed state to an opened state. In this case, too,the tether 16 has a first portion 30 leading to a first tear seam 36,where the first tether portion 30 is connected to a second tetherportion 32. The rear end 34 of the tether 16 is permanently fastened inthis case again on the module or the airbag.

In contrast to the embodiment according to FIGS. 2 to 4 , here thesecond tether portion 32 and the tension means 40 integrally merge intoeach other. This means that the respective part first extends from therear end 34 to the first tear seam 36 and after the first tear seam 36extends at an acute angle back toward the module, where the other end iscoupled to the activation unit 26. This variant can also be realized, ofcourse, in the embodiment according to FIGS. 2 to 4 .

When the activation unit 26 is actuated, the rear end of the tensionmeans 40 is no longer fixed so that no force can be exerted via thetension means 40 upon the first tear seam 36 and the latter remainsstable. This means in turn, however, that the valve unit is opened, forwhen the front wall 18 is moved forward, the tether 16 is subjected totensile load and breaks up the valve unit 68 by undoing the tear seams70.

The overflow opening 66 is free so that gas can flow via the rearchamber 60 into the front chamber 62, and both chambers 60, 62 areinflated. The airbag 10 has the larger volume.

However, when the activation unit 26 is not actuated, the tension means40 exerts, when being tightened, a force upon the first tear seam 36 andresults in destruction thereof. Then the tether 16 is equally destroyedand no force is exerted upon the valve unit 68, the overflow opening 66remains closed, and the second chamber 62 is not inflated. The so-calledsupport wall 80, i.e., the front wall of the second chamber 62, bears onthe front wall 18.

FIG. 6 illustrates the front wall 18 of another airbag 10 in the stateof a small inflation volume. It is evident that in a central region 82the front wall 18 is drawn in. The central region 82 is laterallydelimited by two linear regions 84 and 88 which extend substantially inparallel to each other and are laterally spaced apart from each other.FIG. 7 illustrates a schematic section across the airbag 10. The regions84, 88 are formed by the fact that two holding means 90 juxtaposed andspaced apart from each other act on the front wall 18 and result in thefront wall 18 being inverted as is shown in somewhat exaggerated form inthe section of FIG. 7 . The holding means 90 may be dart-shaped regionsof the front wall 18 or may be stitched-on strips, for example. Theopposite holding means 90 include holes 92 or corresponding eyes whichare shown in FIG. 8 and which are interconnected by a so-called corsetlacing 94.

The corset lacing is defined by a lacing extending in cross shape.

The tether 16 acts on the corset lacing. FIG. 7 shows no more detailsabout how the tether 16 can be destroyed or can remain active. In thisrespect, the preceding Figures can be referred to all of whichillustrate options of designing such mechanism.

When the tether 16 is not destroyed, the corset lacing 94 is notloosened, either, and the airbag retains the smaller configuration shownin FIG. 7 . If, however, the tether 16 is destroyed, because theactivation unit 26 is actuated, the corset lacing 94 can come loose, andthere is available more area of the front wall 18 which can bulgeoutward so that the airbag can adopt the larger airbag volume.

The invention claimed is:
 1. An airbag comprising an outer wall having afront wall and a rear wall, a tether provided inside the airbag, and anelectrically actuatable activation unit for releasing the tether so thatthe latter no longer develops a restraining effect, wherein the airbagadopts a large or a small inflation volume depending on the actuation ofthe activation unit, wherein the tether comprises plural tether portionscoupled to each other via a first tear seam, and to the activation unita tension means is coupled which is coupled at its front end region tothe first tear seam so that, when the activation unit is actuated, thefirst tear seam is destroyed by tension and, during inflation andlacking actuation of the activation unit, the first tear seam remainsintact and the airbag has the smaller inflation volume.
 2. The airbagaccording to claim 1, wherein the tension means is fastened to thetether by the first tear seam.
 3. The airbag according to claim 2,wherein the tension means includes a front end and from there extendsinitially in the direction of the front wall to overlap the tether andin the overlapping region with the first tear seam is fastened to thetether and after the first tear seam is folded over at an acute angle soas to extend in the direction of the activation unit.
 4. The airbagaccording to claim 1, wherein the plural tether portions extend, in theregion where they are fastened to each other, exclusively side by sideand are subjected to tensile load in the opposite direction.
 5. Theairbag according to claim 1, wherein the tension means includes a firstpart which is arranged on the tether with the first tear seam in theregion of its front end or integrally merges into a tether portion inthe region of the first tear seam, wherein the tension means includes asecond part which is fastened, in the region of a rear end of the firstpart, to the first part to be releasable in a controlled manner.
 6. Theairbag according to claim 5, wherein in the region of the rear end ofthe first part the tension means bifurcates into a second part and athird part which extend side by side toward the rear wall and theactivation unit, wherein the second part is permanently fastened to therear end and the third part is coupled by its rear end to the activationunit.
 7. The airbag according to claim 5, wherein the first and secondparts extend, in an overlapping region in which they are fastened toeach other, exclusively side by side when tensioned and are subjected totensile load in the opposite direction, and the third part at its frontend extends in the direction of the front wall, thereby initiallyfastened with a second tear seam at the first and second parts, andafter the second tear seam is folded at an acute angle and extends inthe direction of the activation unit.
 8. The airbag according to claim1, wherein two holding means juxtaposed and spaced apart from each otheract on the front wall and in the interior of the airbag, to whichholding means the tether is coupled, wherein the front wall is invertedby the holding means to form the smaller inflation volume, wherein thetether is released and the inversion is dropped, when the activationunit is actuated.
 9. The airbag according to claim 8, wherein theholding means are connected to each other inside the airbag via a corsetlacing coupled to the tether, when the activation unit is not actuated.10. The airbag according to claim 1, wherein the airbag comprises afront airbag.